Applicant markets (unmanned) vehicles for diverse purposes, such as unmanned transport of containers in harbour areas and vehicles for people, so-called people movers, for transport over and to and from car parks.
The American patent U.S. Pat. No. 5,347,465 describes a system wherein sensors measure the vertical and lateral components of a magnetic field of magnets arranged in the road surface. Using a table showing the relations between the vertical and lateral components of the magnetic field, the transverse distance relative to the magnets can be determined in each case when they are passed. In this known system it is necessary for an automobile equipped with such a system to be situated within certain limits above the (straight or curved) line of magnets. The lateral components of the magnetic field can moreover not be measured precisely because of the terrestrial magnetic field, which can be a particular problem when driving the vehicle through bends.
In the Netherlands patent application 1008587 a line of magnets also has to be followed by the vehicle. The transverse position of the vehicle relative to the line of magnets is determined by the ratio of the two mutually perpendicular horizontal field components. Particularly because of the uncertain outcomes in the case the sensor is situated directly above the magnets, this known sensor system must be combined with an accurate measurement of the path covered, which makes this known sensor system complex and moreover makes it dependent on possible slip and/or other geometric effects. In this known system the possible deviation of the vehicle relative to the line of magnetic marking elements is also limited.